1. Field of the Invention:
This invention relates to an index guided semiconductor laser device that attains laser oscillation in the fundamental transverse mode up to high output power.
2. Description of the prior art:
In recent years, the demand for semiconductor laser devices with high output power has been on the increase in the field of optical disk files, laser printers, and the like. To meet this need, a variety of structures for semiconductor laser devices have been proposed, in which, for example, the thickness of the active layer is as thin as about 0.04 .mu.m in the vicinity of the facets or over the entire area of the resonator, so that the distribution of the optical intensity in the direction vertical to the plane of the p-n junction can be enlarged, increasing the light-emitting area, thereby decreasing the optical output density and decreasing crystal destruction by light absorbance of the facets.
On the other hand, in order to increase the light-emitting area in the direction parallel to the plane of the p-n junction, in the case where the width of the current injection region or the width of the optical waveguide is set to be as wide as 5 .mu.m or more, when the current injected as increased so as to obtain optical output, laser oscillation arises in a high-order transverse mode or the distribution of the optical intensity of the fundamental transverse mode is changed. Laser light produced in this situation cannot be used in an optical disk system for recording information on optical disks or replaying the information by the use of focused beams at the diffraction limit, which are obtained from an optical lens, or for a laser printer for forming latent images with high-density control of focused beams.